Means for burning pulverized fuel



June 24, 1930. F. KOCH 1,766,652

MEANS FOR BURNING PULVERIZED FUEL Filed Dec. 26, 1924 Patented June 24, 1930 P T E N T 'FFIEE FRITZ KOCH, 'OF ST. PAUL, MINNESOTA MEANS FOR BURNING PULVERIZEID FUEL Application filed December 26, 1924. Serial No. 758,250.

My invention relates to improvements in blast feed combustion chambers, and more particularly in the construction and operation thereof, whereby a complete and effecti-ve combustion of a liner or lighter fuel than that ordinarily used isrsecured.

My invention is particularly adaptable to fuel combustion chambers of brick kilns, steam boilers, and the like.

In the accompanying drawings, forming part of this specification:

Figure l is a view in vertical section onthe line l-l of Figure 2 through the combustion chamber of a brick kiln embodying my invention; and

Figure 2 isa view in vertical section taken at right angles to- Figure 1, illustrating my invention embodied in a brick kiln.

Referring to the drawings, A represents a combustion chamber having sloping side walls 2. A grate 3, of a well. known type, is positioned between the lower ends of said side walls. The side Walls, for the purposes of my invention, are sloped at an angle slightly greater than the limiting angle of repose of whatever type of fuel it is desired to use therein Experiment has disclosed that for anthracite dust, or finely divided coke particles known as coke breeze, a slope of about forty-five degrees from the horizontal is suitable. This may be varied to make a slower or faster flow of the fuel particles down said sidewalls as desired. The grate opening is materially less in area than in. ordinary furnace construction. A door opening 4 is positioned to open intozthe combustion chamber above the grate, and a closure therefor is provided by a suitable door 5. Fuel may be fed mechanically or by hand through the opening 4, or the fuel may be wholly or partly fed by a conveyor 6, here shown as an enclosed worm, which conveyor may be arranged in a desired manner in connection with the combustion chamber, as by being tapped through the front wall, as shown in Figure 2 of the drawing.

Below the grate is a chamber 7, preferably, but not necessarily, wider than the grate opening. A pipe 8 is positioned: to be in open communication with chamber 7, as

by being tapped through the front wall thereof, a fan 9 being connected to pipe 8 in a usual manner to force a blast of air into the chamber '7 and upwardly through the grate opening.

Where my invention is used in connection with a brick kiln, as illustrated in the drawings, the combustion chamber A is separated from a brick chamber B by a division wall 10, spaced from the upper furnace wall 11,

to form an intermediate passageway from the combustion chamber to the brick chamber. Bricks 12 are piled within the brick chamber in a usual manner.

In the operation of my invention, a finely divided fuel is employed, such as anthracite dust or coke breeze, so as to be blown upward by a blast of air forced by the fan 9 into the chamber 7 and upwardly through the grate opening. When the finely divided 1 fuel on the grate bars is forced or blown upwardly within the combustion chamber a partial vacuum is formed on either side of the air blast, in conformance to a well known'principle of aerodynamics, and this tends to'spread the fuel out, as indicated' by the arrows, andalso'to diminish-the strength ofthe air blast in its upwardwpaththrough the combustion chamber, as indicated by the shortening of the arrows in the drawings. The spreading'action is further accentuated by'the diverging sides and consequently increasing horizontal cross sectional area of the combustion chamber as greater elevations'therein are reached. The blast is also diverted and diminished by striking the roof of the combustion chambencross currents being set up which rob the blast of its power to support fuel particles. As: a result, as the 'unconsumed particles of fuel approach the upper portion oif:thecombustion chamber, they will, through this spreading and diminishing ofthe airblast, spread out in the form of a spray, and the weight of the fuel particles will overcome he lift- 3.-

ing force ofth'eupward air currents to cause the fuel to fall upon'the inclined walls 2. The fuelithen passes downwardly upon the inclined wa llls by means of gravity, and is returne'd tothe grate opening, where it will currents of the upper portion of the combustion chamber, a falling onto the walls 2, and a slow downward flow over said side walls back to the grates 3, where it is again thrown upward and the action continued as long as the blast is on. As a result, there will be a very complete combustion of fuel,

Lil

and the fuel on the side walls 2 being spread out in a shallow flowing sheet over the inclined faces of the sloping walls 2, will heat these walls to the point of incandescenoe, thereby giving a maximum area of radiation. The constant agitation of the fuel particles prevents the forming of large and troublesome clinkers of the ordinary type, the only clinkers formed being small and round, like marbles. These are removed periodically, as required. Any ash formed is finely pulverized and is, to a large extent, carried by the air stream out of the combustion chamber, in the construction herein shown, passing into the brick chamber B.

The provision of a narrow grate and sloping side walls, provides a storage space for unburned fuel at each line of meeting of a sloping side wall with the grate, as at 15 in Figure 1. The action of gravity on the fuel on the sloping side walls tend to cause the fuel to slide downward onto the grate, while the air blast, coming upward through the grate opening, forces the coal which is upon the grates upwardly. The upcoming blast also acts to hold back fuel at 15 and prevent it from coming at once onto the grate, thus holding it in storage until the fuel on the grates has been blown upward, when a portion of the fuel 15 slides down into the blast, whereupon the process is repeated. The downwardly flowing fuel on the side walls being ignited, after combustion has started, mixes with the fuel which is fed into the combustion chamber as required, each finely divided ignited particle igniting a few of the unignited particles with which it comes in contact upon each recurring cycle of the fuel through the furnace, thereby tending to maintain a fire of a constant degree of in tensity.

I am aware that it is old to use a blast in connection with fuel in a combustion chamber to agitate the fuel and thereby bring about a better combustion, but in such constructions the purposes of my invention are not accomplished. To bring about the results of my invention, it is essential that a sloping wall of a gradual inclination be provided, so that there will be a slow downward flow of fuel across said wall; and that the grate opening be relatively small, so that a blast therethrough will blow the fuel upward in the combustion chamber, and through a diminishing and diverting of the blast in the upper portion of the chamber, will spread the fuel and allow it to drop back upon the sloping wall, while the ash, being lighter, is, to a large extent, carried out of the combustion chamber by the air stream.

I have found, in an experimental use of my invention upon an extensive scale, that fuel of a character not ordinarily usable may be effectively employed in a combustion chamber embodying my present invention, and that a very complete combustion and a high degree of efficiency, not ordinarily attained, is secured, with a resultant material economy of operation.

My invention is based upon the cross sectional relations of air supply, grate bars, and combustion chamber, essentially as portrayed in Figure 1, it being understood that this relation may be applied to any combustion apparatus and that one or more sloping side walls may be provided to feed a common central grate. An increase of the height of the sloping walls of the combustion chamber, will lessen the amount of ash carried away with the departing air stream due to a further retardation of the velocity thereof, and therefore a further lessening of its power to support the ash particles.

\Vhat I claim is:

1. A furnace for burning pulverized fuel, comprising a combustion chamber having a wall therein, said wall having a slope slight ly greater than that of the limiting angle of repose of the fuel particles to be burned in said furnace, a restricted grate area laterally adjacent a lower end of said wall, fuel supply means above said grate to discharge pulverized fuel particles onto said grate, and means below said grate arranged to discharge an air blast upwardly through said grate to raise the fuel particles centrally of said grate, the unconsumed portion of said raised fuel particles being dropped back upon said sloping walls and returned by gravity to the lower end thereof to be supported by said grate and said wall until again raised by said air blast.

2. In a device for burning powered fuel, an enclosure forming a combustion chamber having a side wall of a slope greater than the limiting angle of repose of fuel particles to be used therein, a grate of restricted area laterally adjacent a lower end of said wall, blast means positioned to blow upwardly through said grate, and means to supply powdered. fuel to said grate to be carried upward by the blast and spread over said sloping wall to be returned to said grate fuel having a side wall therein by gravity in continually recurring cycles until comsumed.

3. A furnace for burning pulverized fuel, comprising the combination of a combustion chamber having a Wall therein of a slope slightly greater than the limiting angle of repose of fuel particles to be used therein and a restricted grate area laterally adjacent a lower end of said wall, feed means arranged to feed a supply of pulverized fuel to the upper surface of said grate area, blast means positioned to discharge upwardly through said restricted grate area to support a supply of fuel intermediate said blast and said sloping wall and to carry said fuel upwardly, said blast being diffused and diminished in its upward passage by increase in the cross sectional area of said combustion chamber whereby fuel carried by the blast is dropped upon said sloping wall to be returned by gravity to said supply.

4. A combustion chamber for pulverized fuel having a sloping side wall therein and a restricted grate area laterally adjacent a lower portion of said wall, feed means arranged to feed a supply of pulverized fuel to the upper surface of said grate area, means to direct a blast upwardly through said grate to carry a supply of fuel mixed with ignited particles upwardly and to form a vacuum intermediate said upward blast and said sloping wall to divert the blast to ward the wall to drop the fuel particles and the ignited particles on said sloping wall whereby they are returned by gravity to the bottom portion of said wall and are temporarily retained as a supply of fuel at the bottom portion of said wall to feed into the air blast.

5. A combustion chamber for pulverized fuel, comprising a restricted grate opening, a sloping wall laterally adjacent thereto, feed means arranged to feed a supply of pulverized fuel to the upper surface of said grate area, a discharge opening near the top of said combustion chamber, and means to direct a blast of air upwardly through said grate to support a supply of fuel particles intermediate the upward blast of air and the sloping wall and to blow fuel particles from the face of said fuel supply adjacent the air blast upwardly in said combustion chamber to deposit the fuel particles on the sloping wall, whereby they are returned by gravity to said supply and whereby a portion of the ash particles are carried from the combustion chamber through the discharge openin g A combustion chamber for pulverized with a slope somewhat greater than the limiting angle of repose of fuel particles to be used therein and having a restricted grate adjacent a lower edge of said wall, feed means arranged to feed a supply of pulverized fuel to the upper surface of said grate area, blast means arranged to direct a blast of air upwardly through said grate to carry fuel particles on said grate upwardly in said combustion chamber, said blast being diminished in intensity in its upward passage by the increasing area of the combustion chamber to drop said fuel particles on said sloping wall, whereby they are returned by gravity to the bottom portion of said Wall to be temporarily retained as a supply of fuel at the bottom portion of said wall to feed into said air blast, the ignited particles mixing with adjacent unignited particles to ignite them.

7. A furnace for burning pulverized fuel, comprising a combustion chamber having downwardly converging spaced side walls, a fuel supporting grate connecting the lower portion of the side walls, fuel feeding means for said grate, and air blast means disposed below said grate for agitating and depositing a portion of the fuel upon the side walls of the combustion chamber whereby the fuel is moved by gravity toward said grate and in the path of the recurring cycles until consumed.

In testimony whereof I afiix my signature.

' FRITZ KOCH.

air blast in continually 

